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ICAO Level 5 and 6 Structure: How To Form Complex Irregular Plurals?

ICAO Level 5 and 6 Structure: How To Form Complex Irregular Plurals?

“Aircraft” is the best example of an irregular plural in aviation English and yes, it is the same in the singular (“an aircraft”) and plural (“the aircraft”). No other correct options available. It’s one of the top mistakes non-native English speakers and one of the main reasons one cannot get a high score for the ‘Structure’ section. Today I’d like to take a closer look at the more advanced structures of irregular plural that derive from Latin and Greek.

‘-us’ ending becomes ‘-i’

When a singular word has ‘-us’ ending it will become ‘i’ in the plural: – cactus (singular) -> cacti (plural) or cactuses (plural) In this case both “cacti” and “cactuses” are correct; however, “cactuses” is just the English plural with “-es” at the end. No worries, both are acceptable.

“Cacti and succulents have adapted to grow where there is not much fresh water, in places like deserts.” (BBC)

‘-um’ ending becomes ‘-a’

This is the main rule but in some cases just also the English plural can be found with ‘-um’ ending + ‘-s’. – bacterium – bacteria

“Bacteria are given two names—their genus and species—which are often descriptive of where the bacteria are found or what they look like.” (BBC) – datum – data – millennium – millennia – curriculum – ‘curricula’ but also ‘curriculums’ – planetarium – ‘planetaria’ but also ‘planetariums’ – the second form is more common than the first.

“Children and adults alike visit observatories and planetaria, download images originating from spacecraft in orbit around planets, asteroids and comets, and grab the chance to look through a telescope without hesitation.” (CNN) – stadium – ‘stadia’ but also ‘stadiums’ – the same as ‘planetarium’ – auditorium – ‘auditoria’ but also ‘auditoriums’

‘-ix’ ending becomes ‘-ces’

If a Latin or Greek word has an ‘-ix’ ending it becomes ‘-ces’ in plural according to the main rule. – cicatrix – cicatrices – appendix – appendices – aviatrix – aviatrices – matrix – matrices; matrixes – also acceptable

Amelia Earhart the legendary aviatrix

‘-is’ ending becomes ‘es’

The ‘is’ ending in most cases is transformed into ‘es’ apart from the uncountable words.

Emilia Barska

About me

General English teacher and Aviation English specialist. Devoting her free time to sharing her expert knowledge how to pass an ICAO exam with flying colors. She enjoys reading crime stories, listening to heavy metal music and sipping a vanilla latte.

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